diesel railcar; diesel train; diesel multiple unit
A rail vehicle powered by an internal combustion engine, typically diesel. Common in railway terminology; the English gloss 'diesel multiple unit' is more technical.
Diesel railcars run on this line.
I visited the depot for diesel railcars.
汽車 is a steam train, now often used nostalgically or for older lines, whereas 気動車 is a modern diesel railcar.
Compound of 気 (ki, 'gas' or 'internal combustion') + 動 (dō, 'move') + 車 (sha, 'vehicle'). A straightforward modern coinage for diesel-powered rail vehicles.